Used for the bulk treatment of small parts or pipes (up to several meters long), the closed cleaning system operates in two ways: first, the parts are washed by flooding the cleaning chamber, and second by vapor degreasing in the same chamber. A typical machine is shown below.

The machines are equipped with a side or top entry/exit, together with protected loading/unloading zones. Additionally, the virtually closed loop operation ensures the optimum re-use of solvents.


Schematic of closed cleaning equipment

Cleaning Process Description

  1. Pre-washing - flooding of the cleaning chamber with solvent from Tank Number One.
  2. Evacuation of the Cleaning Chamber and transfer of the solvent back to Tank Number One.
  3. Cleaning/degreasing - either by spray or immersion from Tank Number Two (clean solvent tank) into the Cleaning Chamber. Cleaning power is improved by use of ultrasonic (optional).
  4. Evacuation of the Cleaning Chamber and transfer of the solvent to the Distillation Unit.
  5. Vapor cleaning - pure solvent vapor generated by the distillation unit is sent to the Cleaning Chamber and condenses on the cooler parts. Any residual oil film is completely removed.
  6. Vacuum drying - by applying a vacuum to the Cleaning Chamber the evaporation of the solvent is accelerated.
  7. Ventilation of the Cleaning Chamber to normal atmospheric conditions. The solvent concentration in the Cleaning Chamber is controlled, and the door opens only if the concentration is below the values specified by the VOC Directive.

As an option, the equipment can be operated under a vacuum thus lowering the distillation temperatures and allowing permanent control of the vapor emissions from the cleaning machine.

Vapor Recovery and Workplace Safety
The vapor which is withdrawn from the cleaning chamber is condensed and returned to the clean solvent tank. In addition, the machines are typically equipped with reclaimable active carbon adsorption.

The cleaning machines operate with virtually no emissions and thus respect the health and safety of workers.

Solvent Recovery
Contaminated solvent is purified by means of fine filters which remove particles coupled with distillation. The clean solvent is returned to the tanks while residue is removed from the machine.

This ensures optimum usage of the solvent and also reduces the quantity of waste sent to external treatment companies. It is a modern and economical cleaning process combined with an active contribution to the protection of the environment and safeguard of people's well-being.

Solvent Consumption
Many studies have shown the effectiveness and savings achieved by utilizing the closed cleaning system. One such example is the Perchloroethylene Risk Assessment Report which states:

"In an open cleaning machine, an average use of 7.9 tons of product per year results in up to 5.8 tons of losses through emissions. The remaining 2.1 tons of solvent are collected as used solvent and are sent to specialized companies for waste treatment and recycling."

"For the same volume to be cleaned by a closed system, only 2.35 tons per year is used. Of these 2.35 tons, only 0.14 tons are emitted into the air. The remaining amount of solvent is collected as used solvent and is sent to specialist waste treatment companies and recycling companies to be processed."

The report, on the reduction of emissions of perchloroethylene according to the VOC Directive (1999/13/CE) (30 April 2001), was prepared by the ECSA for the UK Environment Agency.

Meeting the Individual Customer's Needs
No two snowflakes, however similar, are alike. Similarly, customers have different needs to satisfy their particular demands and requirements.

On request, our specialists from SAFECHEM can organize cleaning trials at OEM sites to determine the best technical and economical cleaning solution to meet the individual customer's needs.

The quality of the solvent and continued maintenance of the product for closed cleaning equipment are of paramount importance. Dow has successfully supplied the leading OEMs with chemical know-how, and assisted in their development of cleaning technology for over 40 years.

For detailed information on closed cleaning equipment please contact one of our partner cleaning machine manufacturers.